Apparatus for measuring a micro surface configuration and a method for manufacturing a probe incorporated in this measuring apparatus

ABSTRACT

A probe has a cantilever structure. A piezoelectric element oscillates the probe at or near its resonance frequency. A piezoelectric plate detects a distortion amount of the probe. An actuator adjusts the position of the probe in an oscillating direction so as to stabilize the distortion amount at a constant value. A shifting device adjusts the mutual position between the probe and an objective surface.

BACKGROUND OF THE INVENTION

The present invention relates to a micro surface measuring apparatuspreferably used for measuring a three-dimensional configuration of amachine component in the submillimeter order. For example, thismeasuring apparatus is applicable to the microstructural measurement forthe micro machine parts as well as measurement of an inner surfaceconfiguration for the fuel injector nozzles employed in the internalcombustion engines or the ink jet nozzles of various printers. Morespecifically, the present invention relates to a contact-type microsurface configuration measuring apparatus using a probe directly broughtinto contact with an objective surface to be measured, and also relatesto a related method for manufacturing the probe.

The unexamined Japanese patent application No. Kokai 5-264214 or6-323845 discloses a conventional contact-type micro surface measuringapparatus which is capable of inserting a probe into a narrow or deepportion in a microstructural body or member. Its detailed structure willbe explained, hereinafter.

FIG. 15 shows a first conventional arrangement represented by theunexamined Japanese patent application No. Kokai 5-264214. A probe 101,when actuated by an actuator 102, oscillates in a direction shown by anarrow. The probe 101 is placed closely to a measuring object 103. Themeasuring object 103 is mounted on an X stage 105 which is shiftable inthe X-axis direction. The X stage 105 is mounted on a Z stage 104 whichis shiftable in the Z-axis direction. The Z stage 104 is connected toand driven by a Z-axis feed mechanism 106. The X stage 105 is connectedto and driven by an X-axis feed mechanism 107. A duty cycle measuringdevice 108, interposed between the probe 101 and the measuring object103, measures the duty cycle. A computer 109 controls the Z-axis feedmechanism 106, the X-axis feed mechanism 107, and the duty cyclemeasuring device 108.

According to this arrangement, the actuator 102 causes the probe 101 tooscillate at a predetermined position with a constant amplitude as shownby the arrow in FIG. 15. Electrical conduction between the probe 101 andthe measuring object 103 is detectable as short-circuit current measuredwhen a DC voltage is applied between the probe 101 and the measuringobject 103. The duty cycle measuring device 108 detects the ratio of aconductive duration to the oscillation period.

For example, when the oscillating probe 101 exceeds a certaindisplacement “s” as shown in FIG. 16A, the electrically conductivecondition is maintained between the probe 101 and the measuring object103 as shown in FIG. 16B. FIG. 17 shows a relationship between themeasured duty cycle and the relative distance between the probe 101 andthe measuring object 103. By recording the duty cycle in this manner,the Z-axis feed mechanism 106 is driven to detect the surfaceconfiguration of the measuring object 103.

As understood from FIG. 17, the obtained relationship is not completelyproportional. It is, however, possible to improve the proportionalitywhen the sine wave in the oscillation of the probe 101 is changed to atriangular wave. When the undulation on the objective surface of themeasuring object 103 exceeds the amplitude of the probe 101, the X-axisdrive mechanism 107 is controlled to re-position the measuring object103 for the measurement of the surface configuration of the measuringobject 103.

A second conventional arrangement is based on the AFM (scanning-typeatomic force microscope) techniques which have been rapidly developedand applicable to the micro configuration measurement. The unexaminedJapanese patent application No. Kokai 6-323845 discloses an advanced AFMprobe having a simplified structure and applicable to the microconfiguration measurement for mechanical parts, whereas many ofconventional AFM systems require a large-scale optical system to detectan interatomic force acting on the probe.

FIGS. 18 and 19 show the schematic arrangement of the secondconventional arrangement. A probe 201 is made of an elastic filmy plateof SiO₂ or the like whose size is 200˜300 μm in length, 40˜50 μm inwidth, and 1.8 μm in thickness. A pointed tip 201 a, made of ZnOwhiskers, is bonded at the distal end of the probe 201.

A piezoelectric film 202 b, made of ZnO, is sandwiched betweenelectrodes 202 a and 202 c and located on the surface of the probe 201.The probe 201 is provided on the surface of a silicon wafer 203. FIG. 19shows a practical arrangement of a measuring apparatus using theabove-described probe 201. A sample 206 is placed on a base body 204 viaa Z-axis shift mechanism 205. The probe 201 is attached to the base body204 via an XYZ piezoelectric scanner 207 and a piezoelectric plate 208as shown in the drawing.

According to this practical arrangement, the piezoelectric plate 208causes the probe 201 to oscillate at its resonance frequency. The sample206 approaches the pointed tip 201 a of the probe 201 so closely thatthe oscillating condition of the probe 201 is significantly influencedby an interatomic force. A distortion signal, detectable by thepiezoelectric film 202 b, has the amplitude and phase variable inresponse to the detected oscillation. The position of the XYZpiezoelectric scanner 207 in the Z-axis direction is controlled so as tomaintain the changes in the amplitude and phase of the distortionsignal, thereby detecting the surface configuration of the sample 206.

The AFM detection mode is roughly classified into a contact mode(tapping mode) and a non-contact mode, as introduced in the journal ofsociety of precision engineering, Vol. 62, No. 3, 1996, pp.345˜350. Thenon-contact mode is a measurement mode preferable in that no damage isgiven to the surface of the sample. However, an absorbing layer, such aswater on the sample surface, gives adverse influence in this measurementmode. Thus, the measurement is performed in the vacuum.

On the other hand, the tapping mode is free from such problems derivedfrom the absorbing layer. The AFM measurement according to this mode isgenerally performed in the air and is, therefore, applicable to themicro configuration measurement for many of mechanical parts. FIGS. 20Aand 20B cooperatively show the principle of the contact detection in thetapping mode.

In the condition shown in FIG. 20A, the piezoelectric film 202 b detectsa distortion waveform 211 of the probe 201 whose phase is delayed 90°with respect to the exciting waveform 210 of the probe 201. In thecondition shown in FIG. 20B, the pointed tip 201 a is brought intocontact with the sample 206. In such contact condition, the oscillationof the probe 201 is restricted so as to cause the distortion waveform211 varied in the amplitude. The configuration of the sample 206 is thusmeasured based on the amplitude change of the distortion waveform 211.Although not shown in the drawing, it will be possible to detect theconfiguration of the sample 206 based on the phase change in addition tothe amplitude change.

The above-described two conventional measurements are applicable to theconfiguration measurement of a nozzle hole or a micro groove. However,they have the following problems.

According to the former case represented by the unexamined Japanesepatent application No. Kokai 5-264214, the detection of contactcondition basically relies on the electrical conduction between theprobe 101 and the measuring object 103. Thus, this measuring method isnot applicable to the non-conductive members. Furthermore, even if themeasuring object is electrically conductive, the measurement accuracywill be deteriorated by oxide films covering the surface or dusts on thesurface.

On the other hand, the latter case represented by the unexaminedJapanese patent application No. Kokai 6-323845 has the capability ofdetecting the internal micro configuration regardless of conductivenessof the measuring object.

However, measuring objects are not limited to the ordinary AFM measuringobjects, such as semiconductor surfaces or vacuum processed samples. Forexample, oily or dusty parts will contaminate the AFM probe 201 andrender the measurement useless. Hard or rigid parts will abrade theprobe 201. The measuring object, when its surface has large undulation,may damage the probe.

SUMMARY OF THE INVENTION

In view of the foregoing problems encountered in the prior art, thepresent invention has an object to provide a surface configurationmeasuring apparatus capable of measuring the micro surface configurationof mechanical parts, and also has an object to provide a method formanufacturing the probe used in the surface configuration measuringapparatus.

In order to accomplish the above-described and other related objects,the present invention provides a micro surface measuring apparatus formeasuring the configuration of an objective surface. The apparatuscomprises a probe having a cantilever structure, an oscillating meansfor oscillating the probe at or near its resonance frequency, adistortion detecting means for detecting a distortion amount of theprobe, a positioning means for adjusting the position of the probe in anoscillating direction so as to stabilize the distortion amount at aconstant value, and a shifting means for adjusting the mutual positionbetween the probe and the objective surface.

More specifically, by using the micro electric discharge machining, acemented carbide (sintered hard alloy) is configured into a probe havinga cantilever structure with a pointed tip for measuring theconfiguration of a measuring object. A piezoelectric ceramic, supportingthis probe, causes the probe to oscillate at or near its resonancefrequency. When the oscillating pointed tip is brought into contact withthe surface of the measuring object, the oscillating probe has theamplitude and phase varying in accordance with the degree of thecontact. A piezoelectric ceramic, provided on the probe, produces adistortion signal reflecting the distortion derived from the contactbetween the probe and the measuring object. The servo positioning of theprobe is performed so as to stabilize at least one of the amplitude andthe phase of the distortion signal.

The probe is shifted along the surface of the measuring object whilemaintaining a relative distance between the probe and the measuringobject. Thus, the probe moves along the surface of the measuring object.It becomes possible to measure the configuration of the measuringobject.

In other words, the present invention realizes a micro surfaceconfiguration measuring apparatus capable of stably measuring thesurface of a measuring object regardless of its conductiveness, notadversely influenced by the oxide film or dusts on the surface, with aprobe which is highly resistive in abrasion, highly stable in shape, andhighly durable in corrosion.

The present invention provides a micro surface measuring apparatus formeasuring the configuration of an objective surface, the apparatuscomprising a probe having a cantilever structure, oscillating means foroscillating the probe at or near its resonance frequency, distortiondetecting means for detecting a distortion amount of the probe,positioning means for adjusting the position of the probe in anoscillating direction so as to stabilize the distortion amount at aconstant value, and shifting means for adjusting the mutual positionbetween the probe and the objective surface.

With this arrangement, it becomes possible to measure the configurationof the measuring object regardless of its conductiveness, without beingadversely influenced by the oxide film or dusts on the surface.

It is preferable that the probe has a pointed tip measuring theconfiguration of the objective surface and made of a conductive memberwhich is high in hardness.

Furthermore, it is preferable that the probe is made of a cementedcarbide which is highly resistive in abrasion, highly stable in shape,and highly durable in corrosion. The configuration measurement formechanical parts can be stably performed under actual environments.

Furthermore, it is preferable that the probe is partially or entirelymade of a diamond or BN (boron nitride) sintered material which isharder than the cemented carbide. This is effective to enhance theresistivity in abrasion and the stability in shape. The configurationmeasurement for mechanical parts can be stably performed under actualenvironments.

Furthermore, it is preferable that the probe is manufactured by a microelectric discharge machining. It becomes possible to flexibly form theprobe in various shape.

Furthermore, it is preferable that a deteriorated layer formed duringthe micro electric discharge machining is removed off by the abrasivegrain processing. It becomes possible to obtain the probe highly stablein shape.

Furthermore, it is preferable that the oscillating means includes apiezoelectric member supporting the probe. This provides a stablearrangement for supporting the probe stably.

Furthermore, it is preferable that the oscillating means includes apiezoelectric member provided on the probe. This is effective tosimplify the probe arrangement.

Furthermore, it is preferable that the distortion detecting meansincludes a piezoelectric member provided on the probe. With thisarrangement, it becomes possible to measure the oscillating condition ofthe probe at the position where the oscillatory distortion is maximized.The oscillating condition can be measured with high accuracy.

Furthermore, it is preferable that the distortion detecting meansincludes a strain gauge provided on the probe.

Furthermore, it is preferable that the displacement of the probe isadjustable so as to stabilize a phase variation and/or an amplitudevariation based on the comparison between a signal obtained from thedistortion detecting means and a drive signal of the oscillating means.This realizes a quick and smooth feedback or servo control forpositioning the probe. The stable configuration measurement can berealized.

Furthermore, it is preferable that a voltage is applied between theprobe and the objective surface to detect electric characteristics ofthe objective surface based on a current value measured between theprobe and the objective surface.

Furthermore, it is preferable that the probe and the objective surfaceare magnetic members, and the probe includes a coil to detect themagnetic characteristics of the objective surface based on a magneticflux density modified in accordance with the oscillation of the probe.

Another aspect of the present invention provides a method formanufacturing a probe comprising the steps of adding a distortiondetecting member on a platelike beam material, machining the platelikebeam material into a predetermined beam structure, and removing adeteriorated layer from the resultant beam structure. With thismanufacturing method, it becomes possible to measure the configurationof the measuring object regardless of its conductiveness without beingadversely influenced by the oxide film or dusts on the surface.

Furthermore, it is preferable in the above-described probe manufacturingmethod that the adding step of the distortion detecting member includesthe steps of bonding a piezoelectric member on the platelike beammaterial and machining the bonded piezoelectric member into apredetermined configuration.

Furthermore, it is preferable in the above-described probe manufacturingmethod that the adding step of the distortion detecting member on theplatelike beam material includes the steps of forming a piezoelectricthin film on the platelike beam material and machining the piezoelectricmember into a predetermined configuration during or after the formationof the piezoelectric thin film.

Furthermore, it is preferable in the above-described probe manufacturingmethod that the machining step of the platelike beam material into thepredetermined beam structure is performed by a micro electric dischargemachining. It becomes possible to flexibly form the probe in variousshape.

Furthermore, it is preferable in the above-described probe manufacturingmethod that the removing step of the deteriorated layer from theresultant beam structure is performed by the abrasive grain processing.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will become more apparent from the following detaileddescription which is to be read in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a schematic view showing a probe arrangement in accordancewith a preferable embodiment of the present invention;

FIGS. 2A to 2E are views illustrating the manufacturing processes of theprobe shown in FIG. 1;

FIG. 3 is a schematic view showing the arrangement of a micro electricdischarge machining apparatus used in the manufacturing of the probeshown in FIG. 1;

FIG. 4 is a schematic view showing the arrangement of an abrasive grainprocessing apparatus used in the manufacturing of the probe shown inFIG. 1;

FIG. 5 is a schematic view showing the arrangement of a micro surfaceconfiguration measuring apparatus incorporating the probe shown in FIG.1;

FIG. 6 is a view showing the method for installing the probe into asocket of the micro surface configuration measuring apparatus;

FIGS. 7A to 7D are views illustrating another manufacturing method ofthe probe in accordance with the present invention;

FIGS. 8A and 8B are views showing another probe arrangement inaccordance with the present invention;

FIGS. 9A and 9B are views showing another probe arrangement inaccordance with the present invention;

FIG. 10 is a view showing another probe arrangement in accordance withthe present invention;

FIGS. 11A and 11B are views showing another probe arrangement inaccordance with the present invention;

FIGS. 12A and 12B are views showing another probe arrangement inaccordance with the present invention;

FIGS. 13A and 13B are views showing another probe arrangement inaccordance with the present invention;

FIG. 14 is a view showing another probe arrangement in accordance withthe present invention;

FIG. 15 is a view showing the arrangement of a conventional microsurface configuration measuring apparatus;

FIGS. 16A and 16B are time charts showing the measuring principle of theconventional micro surface configuration measuring apparatus;

FIG. 17 is a graph showing the relationship between theoretical valuesand experimental values in accordance with the measuring method of theconventional micro surface configuration measuring apparatus;

FIG. 18 is a perspective view showing a probe used in the conventionalmicro surface configuration measuring apparatus;

FIG. 19 is a view showing the overall arrangement of the conventionalmicro surface configuration measuring apparatus; and

FIGS. 20A and 20B are views illustrating the measuring principle of theconventional micro surface configuration measuring apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be explained in moredetail with reference to the accompanying drawings. Identical parts aredenoted by the same reference numerals throughout the drawings.

FIG. 1 is a side view showing the probe arrangement in accordance with apreferable embodiment of the present invention. A probe 1 is configuredinto a stepped cantilever arrangement, with a pointed tip 1 a at itsdistal end. The probe 1 has a beam portion 1 b and a proximal portion 1c integrally arranged from the pointed tip 1 a in this order. Apiezoelectric plate 2 extends along the upper surface of the probe 1 inthe region from the beam portion 1 b to the proximal portion 1 c. Theprobe 1 is supported on a support table 4 via a piezoelectric element 3which is provided below the proximal portion 1 c.

A distortion amount of the piezoelectric plate 2 is detectable through apreamplifier 5. A high-voltage amplifier 6 drives the piezoelectricelement 3 fixed on the support table 4. The probe 1 oscillates in anoscillating direction 7. The oscillation frequency is substantiallyidentical with the resonance frequency of the beam portion 1 b of theprobe 1. The piezoelectric plate 2 detects the oscillation of the beamportion 1 b.

According to this arrangement, the pointed tip 1 a of the probe 1approaches the objective surface of a measuring object so closely thatthey are brought into contact with each other at periodic intervals. Bydetecting a reduced amplitude or a changed phase of the oscillation, theconfiguration of the objective surface of the measuring object can bedetected according to the principle of the AFM tapping mode.

The probe 1 is made of a cemented carbide (sintered hard alloy) so thatthe piezoelectric element 3 can effectively resonate the probe 1. At theroom temperature, the cemented carbide is very hard, anti-frictional,highly elastic, and anti-corrosive. Thus, the properties of the cementedcarbide is suitable for the probe used for measuring the configurationof the measuring object.

The cemented carbide is generally difficult to machine due to itshardness. However, to solve this problem, the present invention adopts amicro electric discharge machining. As the cemented carbide is asintered member, it is not subjected to the deformation processing orplastic working. This is preferable in that the cemented carbide has asmall or negligible internal stress and is applicable to the micromachining. Needless to say, it is possible to manufacture a comparableprobe from an appropriate member other than the cemented carbide. Forexample, the cemented carbide can be replaced by a tool steel or athermet which is also used as a tool material, or by a stainless steelor other metallic (e.g., tungsten) materials. However, when any of thesesubstitutional materials is used, the configuration measurement may beinfluenced by its anti-frictional or anti-corrosive properties which areinferior to those of the cemented carbide.

FIGS. 2A to 2E are views showing practical processes for manufacturingthe probe 1 by using the micro electric discharge machining. First, inFIG. 2A, a thin plate material 1′, serving as the probe 1, is 200 μm inthickness, 10 mm in length and 2 mm in width. This thin plate material1′ is formed by grinding a cemented carbide.

Another thin plate material 2′, serving as the piezoelectric plate 2,has a thickness of 20˜30 μm. The thin plate material 2′ is formed bysintering the green sheet of PZT. The area of the thin plate material 2′is substantially identical with that (10 mm×2 mm) of the thin platematerial 1′. Although not shown in the drawing, silver electrodes areformed on the opposed surfaces of the thin plate material 2′. The thinplate material 2′ of the piezoelectric plate 2 is securely bonded on thesurface of the thin plate material 1′ of the probe 1 by using anelectrically conductive adhesive.

Next, as shown in FIG. 2B, only the thin plate material 2′ is processedby the dicing machine to have a thickness of 50 μm. More specifically,by precisely adjusting the cutting depth of the grindstone, only thethin plate material 2′ is planed while the cemented carbide plate isleft without being processed. The reason why the piezoelectric plate 2needs to be processed independently prior to the machining of thecemented carbide plate is that the piezoelectric plate 2 cannot beprocessed by the micro electric discharge machining due to itsnon-conductiveness.

Next, as shown in FIG. 2C, the thin plate material 1′ is processed bythe micro electric discharge machining into the probe 1 with the pointedtip 1 a at its distal end and the beam portion 1 b. The pointed tip 1 ahas a sharp edge with the curvature radius of approximately 1 μm,configured by the micro electric discharge machining.

FIG. 2D is a left side view showing the fabricated probe 1 with thepiezoelectric plate 2. FIG. 2E is a plan view showing the fabricatedprobe 1 with the piezoelectric plate 2. The beam portion 1 b is so thinthat it can be inserted in an inside space of a microstructural member.For example, the width of the beam portion 1 b is 70 μm. The proximalportion 1 c is wider than the beam portion 1 b so that the proximalportion 1 c can be easily installed on the support table 4 via thepiezoelectric element 3. For example, the width of the proximal portion1 c is 2 mm.

The thickness of the beam portion 1 b is 50 μm. While the thickness ofthe proximal portion 1 c is 500 μm. In the bending rigidity, there is alarge difference equivalent to three digits between the beam portion 1 band the proximal portion 1 c. In other words, the beam portion 1 b canbe regarded as a cantilever. The resonance frequency of the bendingvibration occurring in the cantilever is expressed by the followingequation. $\begin{matrix}{f_{n} = {\frac{1}{2\quad \pi}\quad \frac{a_{n}^{2}}{l^{2}}\sqrt{\frac{EI}{m_{l}}}\quad \left( {{a_{1} = 1.875},{a_{2} = 4.694},{a_{3} = {7.855\ldots}}} \right)}} & (1) \\{I = {\frac{1}{12}{bh}^{3}}} & (2)\end{matrix}$

 m_(l)=ρhb  (3)

In the above equations, a_(n) represents a coefficient variable inaccordance with the order of the oscillation, I represents an arealsecond moment of the beam portion 1 b, and m₁ represents the mass of thebeam portion 1 b per unit length. From the above, the primary resonancefrequency f₁ of the beam portion 1 b can be simply expressed by usingthe width b, the thickness h and the length l of the beam portion 1 band the Young's modulus E and the density ρ of the beam material.$\begin{matrix}{f_{1} = {\frac{0.16h}{l^{2}}\sqrt{\frac{E}{\rho}}}} & (4)\end{matrix}$

The probe 1 may be completely made of a cemented carbide whose Young'smodulus is 6.4×10² Gpa and the density ρ is 1.4×10³ kg/m³. In this case,the primary resonance frequency f₁ becomes 24 kHz when the length of thebeam portion 1 b is 1.5 mm.

FIG. 3 shows the micro electric discharge machining apparatus whichperforms the machining processes explained with reference to FIGS. 2A to2E. The micro electric discharge machining apparatus shown in FIG. 3 isbased on the model MG-ED (commercially available from MatsushitaElectric Industrial Co., Ltd.).

In FIG. 3, the apparatus comprises a base 31, an XY stage 32 mounted onthe base 31, a machining tank 33 mounted on the XY stage 32. Themachining tank 33 stores the machining fluid. The machining tank 3 isprovided with a wire guide 35 mounted on a support 34. brass wire 36,which is 100 μm in diameter and held at the distal end of the wire guide35, serves as an electrode for machining the thin plate material 1′ intothe probe 1.

The probe 1 is partly dipped into the machining fluid stored in themachining tank 33. The portion to be processed is disposed adjacent tothe wire 36. The base 31 supports the probe 1 via a Z stage 37 and arotary table 38. In this condition, the thin plate material 2′ of thepiezoelectric plate 2, mounted on the thin plate material 1′ of theprobe 1, is already machined in the predetermined shape. A power source39 is connected between the thin plate material 1′ and the wire 36 heldon the wire guide 35.

According to this arrangement, to perform the electric dischargemachining, a voltage of the power source 39 is applied to a gap betweenthe thin plate material 1′ and the wire 36. The wire 36 wearssignificantly due to the electric discharge energy during the machiningof the thin plate material 1′. Thus, there is a mechanism (not shown)for continuously shifting the wire 36 in a direction normal to the sheetof FIG. 3 so that the portion of the wire 36 subjected to the electricdischarge is always new. Thus, the electric discharge machining isperformed according to the so-called WEDG method which attains themachining accuracy of a sub μm level.

Then, the rotary table 38 accurately adjusts the angle of the thin platematerial 1′ in accordance with advancement of the electric dischargemachining. The XY stage 32 and the Z stage 37 cooperate to adjust thepositional relationship between the thin plate material 1′ and the wire36 during the electric discharge machining. This arrangement makes itpossible to completely automate the above-described processes of FIGS.2C to 2E which require the complicated three-dimensional machining.

The electric discharge machining basically utilizes the thermal energyof S electric discharge to remove or cut the material. Thus, in themicro electric discharge machining, a deteriorated layer 1″ remains onthe processed material. When the cemented carbide is processed by theelectric discharge machining, the processed surface of the cementedcarbide usually lacks the bonding phase because the Co metal in thebonding phase has a low melting point while the WC powders serving asthe main material have a high melting point. In this deterioratedcondition, the WC powders are easily removed off the processed surface.If such a cemented carbide with a deteriorated surface is directly usedfor the probe 1, the pointed tip of the probe 1 will be deformed duringthe measurement. This results in errors in the measurement.

To effectively remove the deteriorated layer 1″ off the processedsurface of the plate 1, the plate 1 is brought into contact with thesurface of a metallic wear plate 22. A slurry 21 containing abrasivegrain is applied on the surface of the wear plate 22 as shown in FIG. 4.To cause a relative motion between the wear plate 22 and the probe 1, anoscillation generator 23 can generate the oscillatory movement of 50 Hzin frequency and 5 μm in amplitude in an arbitrary direction. The wearplate 22 is made of a relatively soft material, such as tin or copper.Although not shown in the drawing, there is a mechanism for positioningthe probe 1 with respect to the wear plate 22. A current detectingcircuit, including a DC power source 24, an ammeter 25, and a resister26, is connected between the probe 1 and the wear plate 22 to detect thecontact condition between the probe 1 and the wear plate 22. Thepositioning mechanism performs the positioning operation for the probe 1in accordance with the current value measured by the ammeter 25.

Hereinafter, details of the configuration measurement using themanufactured probe 1 will be explained. FIG. 5 is a schematic viewshowing an overall arrangement of the micro surface configurationmeasuring apparatus equipped with the probe 1. In FIG. 5, a base 41mounts an X stage 42, a Y stage 43, and a Z stage 44 in this order. Amain CPU 45 controls these stages 42 to 44. A measuring object 46 isplaced on the top of the stacked stages 42 to 44 so that it is shiftablein a three-dimensional space.

The accuracy in the positioning the stages 42 to 44 directly leads tothe error in the configuration measurement. This embodiment uses abuilt-in linear scale for accurately managing the position of eachstage. The main CPU 45 controls a rotary table 47 provided at an upperportion of the base 41.

An actuator 48 is attached to the rotary table 47. The probe 1 with thepiezoelectric plate 2 is attached to the actuator 48 via the supporttable 4 and the piezoelectric element 3. The actuator 48 moves in thedirection 7 identical with the oscillating direction of thepiezoelectric element 3. The accuracy of the actuator 48 in thepositioning operation is in the order of 1/100 μm. Its dynamic range isas wide as the movable range of 100 μm. The arrangement of thisembodiment comprises both the piezoelectric element and a displacementenlargement mechanism. As the actuator 48 is attached to the rotarytable 47, the oscillating direction 7 of the probe 1 is variable in360°.

The roundness of the rotary table 47 gives influence to the error in theconfiguration measurement. To minimize the error, the rotary table 47uses an air bearing which is highly accurate. A signal, representing adistortion of the piezoelectric plate 2, is sent from the piezoelectricplate 2 to a sub CPU 51 via the preamplifier 5 and an orthogonaldetector 49. The sub CPU 51 generates a command voltage signal sent tothe piezoelectric element 3 via a VCO 50 and the high-voltage amplifier5. In response to this drive signal, the piezoelectric element 3 causesthe oscillatory movement.

The sub CPU 51 not only controls the actuator 48 but also sends a signalto the main CPU 45. The signal generated from the VCO 50 is sent to theorthogonal detector 49, too.

Furthermore, in the micro configuration measurement, it is generallydifficult to shift the probe 1 to a measuring point on the measuringobject 46 by simply relying on the naked eyes. This is why a microscope54 is equipped for the alignment. The measuring object 46 is shiftedunder the microscope 54 by the X stage 42 so that the coordinates of themeasuring point can be measured through the microscopic screendisplaying the measuring object 46. Using the measured coordinates, themeasuring point can be accurately positioned under the probe 1.

According to this embodiment, the above-described micro surfaceconfiguration measuring apparatus operates in the following manner.

First, the VCO 50 generates a constant frequency signal based on thecommand voltage signal fed from the sub CPU 51. The constant frequencysignal is sent to the piezoelectric element 3 via the high-voltageamplifier 6. The piezoelectric element 3 oscillates in the direction 7.This oscillatory movement is transmitted to the probe 1. In response tothe vibration transmitted to probe 1, the piezoelectric plate 2 producesthe distortion signal which is entered into the orthogonal detector 49via the preamplifier 5.

The orthogonal detector 49 measures a phase shift between the distortionsignal and the output signal of the VCO 50. The measured phase shift issent to the sub CPU 51. In this case, the output frequency of the VCO 50is set to a predetermined value so that the probe 1 can cause theresonant oscillation. In other words, the 90° phase difference isprovided between the output signal of the preamplifier 5 and the outputsignal of the VCO 50. The resonance frequency, being set in thisembodiment, is approximately 25 kHz. When any variation is found in thecommand voltage signal supplied to the VCO 50, it reflects the contactcondition of the probe 1.

Alternatively, it is possible to set the output frequency of the VCO 50at a predetermined value so that the probe 1 can cause the resonantoscillation, and the sub CPU 51 records the phase relationship or anamplitude ratio between the output signal of the preamplifier 5 and theoutput signal of the VCO 50. In this case, any change in the phaseand/or amplitude reflects the contact condition of the probe 1.

The amplitude of the oscillation is approximately 100 nm at the distalend of the probe 1. As the probe 1 is regarded as a cantilever, it ispossible to estimate the contact pressure of the probe 1 based on theamplitude measured at the distal end thereof. More specifically, thefollowing equation defines a force f that needs to be applied to thedistal end of a cantilever to cause a distortion δ statically at thisdistal end. $\begin{matrix}{f = {\frac{3{EI}}{l^{3}}\delta}} & (5)\end{matrix}$

When the probe 1 is made of a cemented carbide and the beam portion 1 bis 1.5 mm in length, 50 μm in thickness, and 70 μm in width, the force frequired for causing a distortion of 100 nm is approximately 3 mg. Undersuch a small contact pressure, filmy water existing on the surface ofthe measuring object may cause a measuring error due to its surfacetension. To eliminate this error, an appropriate arrangement (not shown)is provided for supplying dry air to the surface of the measuring objectso as to remove the water or moisture component from the surface of themeasuring object.

When the probe 1 is brought into contact with the measuring object 46through the positioning operation using the stages 42 to 44, thecondition of the probe 1 slightly deviates from the resonantoscillation. This deviation is detectable as an output of the orthogonaldetector 49 and is sent to the sub CPU 51.

The sub CPU 51 controls the actuator 48to correct or eliminate thisdeviation. Through such a feedback or servo control, the probe 1 can bealways shifted along the surface of measuring object 46 whilemaintaining a negligible clearance therebetween. Thus, the configurationof the measuring object is detectable from the composite movementresulting from the three-dimensional motion of the stages 42 to 44 andthe rotational motion of the actuator 48 mounted on the rotary table 47.

The signal sent from the sub CPU 51 to the main CPU 45 is a signalrepresenting the position of the actuator 48. As the main CPU 45 managesall of the position data of the stages 42 to 44 and the rotary table 47it is possible for the main CPU 45 to perform necessary calculationsbased on the position data and display the measuring result.

The apparatus shown in FIG. 5 includes a current detecting circuitcomprising a DC power source 52 and an ammeter 53. Although it isdispensable for the configuration measurement, providing this circuitmakes it possible to know the electric properties of the objectivesurface, such as local oxidation, dirt or stain, or locally deterioratedconductivity, based on the current measured by the ammeter 53. Thiselectric measurement can be done simultaneously with the configurationmeasurement.

For example, it becomes possible to detect the non-conductive depositcontained in a metallic part, the abrasive grain sunk into the workpieceduring the grinding operation, or the oxidation film partly formed onthe metal surface.

Furthermore, besides the measurement of the electric properties, it ispossible to measure the magnetic properties simultaneously with theconfiguration measurement. For example, it is assumed that the measuringobject 46 is made of a magnetic member. In this case, a magnetic circuitis formed between the measuring object 46 and the probe 1 which is aferromagnetic substance. It is preferable to provide a coil wound aroundthe proximal portion 1 c of the probe 1. The magnetic flax, whenmodified by the oscillation of the probe 1, can be measured by thiscoil. If the ferromagnetism of the probe 1 gives adverse influence tothe measurement, it will be possible to obtain a non-magnetic probe bymodifying the material of the bonding phase of the cemented carbide.

FIG. 6 shows the method for installing the probe to the micro surfaceconfiguration measuring apparatus. The probe, used in the micro surfacemeasuring apparatus of this embodiment, is a mechanical cantilever whoselength is limited within a certain range in view of the strength incomparison with its thickness. In general, the probe needs to be thinand short enough for measuring a thin hole, on the other hand, needs tobe thick and long enough for measuring a deep place. Hence, a pluralityof probes are prepared beforehand and selectively used in accordancewith the measuring object. Therefore, it is important to provide asimplified attaching and/or detaching arrangement for exchanging theprobes.

In FIG. 6, the support table 4 is a ceramic flat plate. Electrodes 80,81 and 82 are formed on the upper surface of this support table 4. Theelectrode 80 is directly connected to a lower electrode (not shown) ofthe piezoelectric element 3. To drive the piezoelectric element 3,electric power is supplied to the electric electrode 80. The electrode81 is grounded to maintain an upper electrode (not shown) of thepiezoelectric element 3 and the probe 1 at a ground potential. Theelectrode 82, connected to the piezoelectric plate 2, serves as anoutput terminal of the distortion signal obtained from the piezoelectricplate 2. A socket 85 has a receiving bore which faces downward when thesocket 85 is fixed to the actuator 48 of the micro surface configurationmeasuring apparatus. The probe 1 is attached to the socket 85 byinserting the support table 4 into the receiving bore of the socket 85.The electrodes 80, 81 and 82 formed on the surface of the support table4 are brought into contact with corresponding electrodes 83 formed inthe receiving bore when the support table 4 is completely engaged withthe socket 85. Thus, the electrodes 80, 81 and 82 are electricallyconnected to other electric components of the micro surfaceconfiguration measuring apparatus. The socket 85 is equipped with a lockmechanism (not shown) for securely holding the support table 4.

The manufacturing cost of the probe may not be low according to themanufacturing method disclosed in the above-described embodiment,because this manufacturing method includes the bonding of thepiezoelectric material onto the probe material as well as the machiningof both the piezoelectric material and the probe member. The followingembodiment provides a non-expensive manufacturing method.

First, as shown in FIG. 7A, a prepared probe material 1″ is grindingfinished. This probe material 1″ is 0.2 mm in thickness and has a squareshape of 20 mm×20 mm. A piezoelectric plate material 2′, havingsubstantially the same size as that of the probe material 1″, is bondedon the surface of the probe material 1″ in a face-to-face relationship.Silver electrodes (not shown) are formed on opposed surfaces of thepiezoelectric plate material 2′. The bonded unit of the materials 1″ and2′ is then configured into the shape shown in FIG. 7B through the sandblasting. A plurality of piezoelectric plates 2 are formed on thesurface of the probe material 1″. According to the sand blasting,abrasive grain is accelerated by the pressurized air. During the sandblasting, the piezoelectric plate is subjected to the pressurized air.To prevent the piezoelectric plate 2 from removing off the probematerial 1″ due to the pressurized air, having a low aspect ratio ispreferable. In this respect, the minimum pattern size of thepiezoelectric plate 2 is 200 μm.

FIG. 7C is a plan view showing a plurality of divided probe materials 1′which are obtained by cutting the probe material 1″ by the wire cutelectric discharge machining. One piezoelectric plate 2 is mounted oneach divided probe material 1′.

The succeeding machining processes are identical with those explainedwith reference to FIG. 2, and performed so as to obtain the probes oneafter another. The piezoelectric plate 2 processed by the sand blastinghas a width of 200 μm which is wider than that of the piezoelectricplate 2 processed by the dicing. As shown in FIG. 7D, the probe 1 has awide portion 1 d as part of the beam portion 1 b. As expressed by theequation 4, the length 1 and the thickness h of the probe 1 are theparameters determining the resonance frequency of the probe 1. However,the width b has no influence to the resonance frequency. Accordingly,providing the wide portion 1 d gives no adverse influence to theproperties of the probe 1.

As described above, this embodiment makes it possible to perform thebonding process, the sandblasting, and the wire cut electric dischargemachining for forming numerous probes. Thus, 10 to 20 probes can bebatch processed at a time. This improves the manufacturing efficiency.However, the processes shown in FIGS. 7D and 7E need to be doneindependently for each probe by using the micro electric dischargemachining. This may be advantageous in that numerous kinds but smallnumber of probe configurations can be provided to satisfy variousmeasuring requirements from the users.

The present invention provides various probe arrangements.

FIG. 8A is a side view showing the probe material 1′ of the probe 1FIG.8B is a side view showing the accomplished shape of the probe 1fabricated from the probe material 1′. The probe material 1′ comprises acemented carbide 27 and a diamond layer 28 which are stacked andsintered together. Like the cemented carbide 27, the sintered diamondlayer 28 has a bonding phase of cobalt. Thus, the electric dischargemachining is preferably applied on the sintered diamond layer 28 tofabricate the probe 1 by using the method explained with reference toFIGS. 2A˜2E or 7A˜7D. As shown in FIG. 8B, the fabricated probe 1 has apointed tip 1 a made of a sintered diamond. As a result, the pointed tip1 a has excellent anti-frictional property which is superior to that ofthe cemented carbide. The life of the probe can be extended greatly. Thesintered diamond layer can be replaced by a sintered BN (boron nitride)having the metallic bonding phase. Although the beam portion 1 b is madeof the cemented carbide 27, it is possible to use a beam portion 1 bmade of a sintered diamond material. In this case, the beam portion 1 bmay have poor durability against an impact force. It is thus preferablethat the probe has a sufficient thickness.

FIG. 9A is a side view showing another arrangement of the probe 1. FIG.9B is a plan view showing the same. According to this arrangement, asecond piezoelectric plate 51 is bonded on a reverse surface of theprobe 1. The second piezoelectric plate 51 is a substitute for thepiezoelectric element 3. In other words, the piezoelectric element 3 canbe omitted. Needless to say, it is possible to dispose the secondpiezoelectric plate 51 at both sides of the piezoelectric plate 2instead of placing it on the reverse surface.

By adopting this arrangement, the piezoelectric element 3 can be removedfrom the measuring loop. It is effective to prevent any measuring errorsderived from the shape drift or thermal deformation of the piezoelectricelement 3.

As shown in FIG. 10, to eliminate measuring errors derived from thepiezoelectric element 3, it is possible to use the piezoelectric plate 2itself as a means for oscillating the probe 1. According to thisarrangement, the piezoelectric plate 2 is connected to an impedancemeter 62 to read the change in the impedance value which reflects thecontact condition of the oscillating probe 1. However, according to thisarrangement, the measuring sensitivity may deteriorate when thepiezoelectric plate 2 is downsized with a thin thickness. Thus, it ispreferable that the piezoelectric plate 2 has an area larger than 1 mm².

FIG. 11A is a side view showing another arrangement of the probe 1. FIG.11B is a plan view of the same. According to this arrangement, thepiezoelectric plate 2 is replaced by a strain gauge 61. The strain gauge61 has substantially the same function as that of the piezoelectricplate 2.

The strain gauge 61 may be a metallic type or a semiconductor type. FIG.12A is a side view showing another arrangement of the probe 1. FIG. 12Bis a plan view of the same. According to this arrangement, apiezoelectric thin film 71 is formed on a surface of the probe 1. Thepiezoelectric thin film 71 has substantially the same function as thatof the piezoelectric plate 2.

The piezoelectric thin film 71 can be manufactured by using the sol-gelmethod, introduced by K. R. Udayakumar et al. in FERROELECTRIC THIN FILMULTRASONIC MICROMOTORS, IEEE, 1991 or by using the sputtering methodintroduced by T. KAMADA et al. in Mat. Res. Soc. Syp. Proc. Vol. 433,pp377 (1996).

More specifically, the lapping is applied on the surface of the probe 1made of a cemented carbide to improve the surface roughness. A Pt/Tilayer is formed on the finished surface of the probe 1. Then, thepiezoelectric thin film 71 is formed on the Pt/Ti layer. Then, theetching is applied on the piezoelectric thin film 71 to leave thenecessary portion. Then, a distortion detecting electrode 72 is formedon the piezoelectric thin film 71 for detecting the distortion.

The thickness of the piezoelectric thin film 71 is 1˜3 μm at maximum.There are some merits which are not obtained when the bulkypiezoelectric plate 2 is used. First, as the thickness of thepiezoelectric thin film 71 is sufficiently thin compared with that ofthe probe 1, it becomes possible to prevent the probe from bending dueto the bimorph effect induced by a thermal expansion difference betweenthem. Furthermore, the pattern forming by the etching makes it possibleto reduce the thickness of the piezoelectric thin film to the level of10 μm. This is effective in miniaturizing the probe. Furthermore, thisarrangement does not require the electrically conductive adhesive whichis used in the above-described embodiment for bonding the bulkypiezoelectric plate 2. The internal damping with respect to thevibration is reduced, while the Q value in the resonance of the probe isincreased. Thus, the sensitivity in the detection of the probe can beimproved.

FIGS. 13A and 13B show another probe arrangement in accordance with thepresent invention. According to this arrangement, two distortiondetecting electrodes 72 a and 72 b are formed on the piezoelectric thinfilm 71. FIG. 13A is a left side view of the probe 1, while FIG. 13B isa plan view of the same. In FIG. 13A, the probe 1 oscillates in theoscillating direction 7. It is expected that the probe 1 is brought intocontact with the measuring object in the sensing direction 73. However,there is a possibility that the probe 1 may be brought into contact withthe measuring object in another sensing direction 74. In this case, suchan unexpected contact is detectable from the change occurring in theresonant condition. However, it is difficult to discriminate thedifference between the sensing directions 73 and 74. To solve thisproblem, this arrangement uses two distortion detecting electrodes 72 aand 72 b which are separated from each other. The distortion detectingelectrodes 72 a and 72 b cooperate to detect the twist of the beamportion 1 b so as to identify the difference between the sensingdirections 73 and 74.

FIG. 14 shows another probe arrangement in accordance with the presentinvention. According to this arrangement, right-and-left electrodes 76are provided in addition to upper-and-lower electrodes 75. An oscillator78 supplies an exciting signal of frequency f1 between theupper-and-lower electrodes 75 to resonate the probe 1 in one sensingdirection 73. Another oscillator 77 supplies an exciting signal offrequency f2 between the right-and-left electrodes 76 to resonate theprobe 1in the other sensing direction 74. The thickness and the width ofthe beam portion 1 b are appropriately designed so that the resonancefrequency of the beam portion 1 b is differentiated in the sensingdirection 73 and in the sensing direction 74.

As a result, the distortion detecting signal obtained from thepiezoelectric plate 2 is separable into two frequency components whichare detected through two orthogonal detectors 49 (not shown)independently as signals representing the contact conditions in thesensing directions 73 and 74. As easily assumed from this arrangement,it is possible to provide additional electrodes on the remaining twosurfaces of the piezoelectric element 3. An exciting signal of frequencyf3 is applied between these electrodes to oscillate the beam portion 1 bin the direction 79. With this arrangement, it becomes possible toindependently detect the contact condition in the direction 79.

The above-described probes can be incorporated in the micro surfaceconfiguration measuring apparatus explained in the above-describedembodiment to measure the configuration of a measuring object.

As apparent from the foregoing description, the present inventionprovides the probe having a cantilever structure and made of a cementedcarbide. The probe has the pointed tip used for measuring theconfiguration of a measuring object. The piezoelectric element supportsthis probe and oscillates the probe at or near its resonance frequency.When the pointed tip of the oscillating probe is brought into contactwith the objective surface, the amplitude and the oscillatory phase ofthe probe vary in accordance with the degree of the contact. Thepiezoelectric plate, provided on the surface of the probe, produces thedistortion signal representing the distortion occurring on the probe.The actuator performs the feedback or servo control to adjust theposition of the probe in the oscillating direction, thereby stabilizingthe oscillatory condition of the probe. While maintaining the stabilizedoscillatory condition, the position of the probe with respect to themeasuring object is continuously changed by driving the stages and therotary table. Thus, the probe moves along the undulated surface of theobjective surface. As a result, the configuration of the measuringobject is measured.

According to this arrangement, it becomes possible to provide a microsurface configuration measuring apparatus capable of stably measuringthe objective surface regardless of its conductiveness, not adverselyinfluenced by the oxide film or dusts on the surface, with the probewhich is highly resistive in abrasion, highly stable in shape, andhighly durable in corrosion.

This invention may be embodied in several forms without departing fromthe spirit of essential characteristics thereof. The present embodimentsas described are therefore intended to be only illustrative and notrestrictive, since the scope of the invention is defined by the appendedclaims rather than by the description preceding them. All changes thatfall within the metes and bounds of the claims, or equivalents of suchmetes and bounds, are therefore intended to be embraced by the claims.

What is claimed is:
 1. A method for manufacturing a probe comprising thesteps: adding a distortion detecting member on a platelike beammaterial; machining said platelike beam material into a predeterminedbeam structure; and removing a deteriorated layer from a surface of saidpredetermined beam structure.
 2. The probe manufacturing method inaccordance with claim 1, wherein said adding step of said distortiondetecting member includes the steps of bonding a piezoelectric member onsaid platelike beam material and machining the bonded piezoelectricmember into a predetermined configuration.
 3. The probe manufacturingmethod in accordance with claim 1, wherein said adding step of saiddistortion detecting member on the platelike beam material includes thestep of forming a piezoelectric thin film on said platelike beammaterial and machining the piezoelectric member into a predeterminedconfiguration during or after the formation of said piezoelectric thinfilm.
 4. The probe manufacturing method in accordance with claim 1,wherein said machining step of said platelike beam material into thepredetermined beam structure is performed by a micro electric dischargemachining.
 5. The probe manufacturing method in accordance with claim 1,wherein said removing step of said deteriorated layer from saidpredetermined beam structure is performed by abrasive grain processing.